Above: X-ray, Ultraviolet (w2, m2,
w1 filters) and visible (B,V,u,b,v,g',r',i') light curves showing
the declining brightness of GRB 130427A over a period of a few
weeks. In this plot LT and Faulkes-North r' and i'-band data points
are coloured red and yellow. The discovery was triggered in the
X-ray (black data points). [Full size
image]

On April 27, 2013 many of the world's astronomers observed the
brightest Gamma-Ray Burst (GRB) ever detected by the Swift
satellite. Named GRB 130427A, it was one of the most energetic nearby
events ever encountered. At a redshift of z = 0.3399, which
corresponds to a distance of only 3.6 billion light years, GRB
130427A was a truly unique and extraordinary "nearby
monster".

GRBs trace the most energetic explosions in the Universe. Some are
believed to occur after the merger of two compact objects - a pair of
neutron stars or a neutron star and a black hole. Others may be
caused by the collapse of a rapidly-rotating massive star. The former
are classified as short-GRBs, due to the very limited durations
of their gamma-ray emission (less than a few seconds). The latter are
classified as long-GRBs, since the mean duration of their
"prompt emission" phase lasts longer than a few tens of seconds.

GRB 130427A belongs to the second class of object (its duration
lasted longer than 160 sec) and was probably the result of the
collapse of a star 30-40 times the mass of the Sun with an intrinsic
luminosity of 3 x 1053 erg/sec (for comparison the
luminosity of the Sun is a mere 3.8 x 1033 erg/sec, one
hundred billion billion times less!).

Ground-based facilities such as the Liverpool Telescope and
Faulkes-North (a sister telescope to the LT) were used to monitor the
optical behaviour of GRB 130427A, from very soon after the explosion
up to relatively late times (see the attached light curves). These
monitoring observations tracked the evolution of the burst emission
with a high cadence, from the initial "prompt" phase to the
"afterglow" phase (Maselli et al. 2014).

Careful analysis of these multi-wavelength data (which include GeV,
Gamma-ray, X-ray, ultra-violet and optical bands) showed that the
relatively nearby GRB 130427A had similar properties to the most
luminous and much more distant high-redshift GRBs. This result
suggests that a common central engine may be responsible for
producing GRBs in both the contemporary, nearby universe and in the
much more distant, early universe, as well as over the full range of
GRB isotropic energies. Moreover, "monsters" like GRB 130427A seem to
be strictly connected with Supernovae explosions (GRB 130427A was
subsequently found to be associated with SN 2013cq) which, prior to
these observations, was observed to be the case for only the weaker
long-GRBs (Melandri et al. 2014).

Clearly, with their rapid response capabilities, robotic telescopes
like the Liverpool Telescope are crucial to our understanding of the
rapid evolution of these remarkable transient objects, both at early
times during the prompt/afterglow phase and at later times as the GRB
afterglow fades and the SN phase emerges.